In a large mixing bowl, combine flour and salt.

Whisk together sour cream and egg in a separate small bowl. Pour this into the flour mixture.

Stir until the dough comes together, then knead it on a floured surface for about 5 minutes until smooth and elastic. (If it’s sticky, add a bit more flour, 1 tablespoon at a time.)

Wrap the dough in plastic wrap and let it rest at room temperature for at least 30 minutes.

Heat one tablespoon of butter in a skillet over medium heat. Add a finely chopped small onion and cook until softened and translucent, for about 3–4 minutes. Remove from heat and let cool slightly.

Place shredded turkey into a food processor and pulse briefly to make it finer and smoother. Avoid over-processing; you want it soft but not a paste.

Add the ricotta, herbs, parmesan cheese, cooked onion, and salt and pepper to the turkey meat, and pulse a few more times to mix the ingredients.

Transfer the processed turkey filling to a large bowl. Taste and adjust the seasoning if needed.

Roll out the rested dough on a lightly floured surface until it’s about 1/8 inch thick.

Cut out as many circles as possible using a 3-inch round cutter or the rim of a glass. Gather the scraps, re-roll, and cut additional circles until all the dough is used.

Place about one teaspoon of the turkey filling in the center of each dough circle.

Lightly moisten the edge of each circle with a dab of water, then fold it over to form a half-moon shape.

Press the edges firmly to seal, then crimp with a fork (or use a pierogi press) to prevent leaks during cooking.

Bring a large pot of salted water to a boil. Drop in a few pierogi at a time, being careful not to overcrowd the pot.

Boil until they float to the top, then cook for another 2–3 minutes to ensure the filling heats through.

Use a slotted spoon to remove the pierogi from the pot and transfer them to a plate. Repeat until all pierogi are cooked.